Finely divided metals, as well as metal oxides and hydroxides, have a variety of uses, such as in the construction of positives in electrochemical energy supplies and as catalysts. A variety of techniques have been used for the production of these materials, that disclosed by K. N. Brown in U.S. Pat. No. 3,003,935 being illustrative of the manufacture of argentous oxide. Brown discloses a cell using two electrolytes, a silver ingot anode and a steel cathode. The silver anode is placed in an electrolyte of 10% NaNO.sub.3 adjusted to a pH of 9-11 with an alkali such as sodium hydroxide or potassium hydroxide. The steel cathode is immersed in a second electrolyte, namely, the catholyte, in a cathode cup containing an alkali such as sodium hydroxide. At the anode, the silver is converted into argentous ions, which react with hydroxyl ions in the alkaline solution to form Ag.sub.2 O, which falls to the bottom of the vessel. The bottom of the vessel stops so that the Ag.sub.2 O moves to the lowest portion thereof, from which it can be withdrawn through an appropriate valve.
At the steel cathode, hydrogen is generated. Brown expresses the concern that nitrate ion reaching the cathode may be reduced to ammonia, which, in contact with the argentous oxide, could form the extremely explosive silver azide. Consequently, Brown finds it necessary to maintain the level in the catholyte compartment of the cell higher than that of the anolyte, so that there is a tendency for the catholyte to flow into the anolyte instead of vice versa, thereby preventing nitrate ion from reaching the cathode.
By the technique disclosed by Brown, argentous oxide varying in particle size from 0.7 to 1.2 microns is obtained.
Needless to say, the requirement of a catholyte cup and maintaining the level of the electrolyte in the catholyte cup above that in the remainder of the cell introduces difficulties as well as restrictions on the process. Also, the particle size range obtained by the process of Brown is limited. Furthermore, although Brown does not comment on the point, there is a substantial overvoltage involved in the evolution of hydrogen on a steel cathode, this overvoltage, when multiplied by the current used for the production of the argentous oxide, being a measure of the energy wasted in the process.
It would therefore be desirable that a process be available which provides for a wider range of particle sizes produced by said process, which avoids the complexities of the Brown cell construction, and which eliminates the overvoltage loss at the cathode. In addition, Brown discloses a process which produces only argentous oxide, whereas oxides of other metals, and particularly, finely divided metal powders obtained from such oxides are also valuable, so that a process which makes a variety of oxides, hydroxides and metals in finely divided form available would be highly desirable.